1. Field of the Invention
The present invention relates to a field emission device used for a display, an electron beam exposure apparatus using converged electron beams, and the like.
2. Related Background Art
A field emission type cold cathode device (hereinafter “field emission device” will be referred to) is expected to be applied for various kinds of electronics such as an image display apparatus, an electron microscope, an electron beam exposure apparatus, and the like. In these apparatuses, even after sale, it is necessary to maintain the quality of products by prolonging the lifetime of the field emission device. However, since the field emission device generally has only one portion that causes emission (emits electrons), it was difficult to increase the lifetime of the device. Therefore, a large number of techniques for improving the lifetime of the device have been proposed. For example, JP 5 (1993)-12986A discloses a field emission device in which plural electron emission portions are electrically connected in series and the electron emission portions contributing to emission of electrons is changed by using a conductive member and heat.
FIG. 15 is a schematic view showing this field emission device. In FIG. 15, reference numerals 1 and 2 denote a cathode electrode and an anode electrode, respectively; 3 denotes a particulate film including an electron emission material; 4 denotes an insulating substrate; 5a denotes an electron emission portion; 6a denotes a phosphor target; 7 denotes a light emitting portion; and 8a denotes a conductive member. As shown herein, plural electron emission portions 5a are disposed between a pair of electrodes. In the vicinity of these electron emission portions 5a, conductive members 8a are disposed to form a field emission device. In this field emission device, the conductive member 8a is melted by heat supplied by irradiation with infrared rays to short-circuit the cathode electrode 1 and the anode electrode 2. Thus, the electron emission portion 5a is changed.
However, in this device, the electron emission portions 5a can be changed only in the manufacturing process. Therefore, if a problem occurs in the field emission device after products using this device come on the market, such a problem cannot be resolved appropriately. Consequently, it has not been possible to increase the lifetime of the device. Furthermore, in this device, also in the manufacturing process, since the electron emission portions 5a are connected in series, the number of components such as an electrode is increased, thereby prolonging the number of manufacturing steps and reducing the yield. Furthermore, when the electron emission portions are changed, in order to identify a defective part, a microscope, etc. is needed. Also, it is also necessary to supply heat successively from the outside by laser irradiation, etc. Thus, this device was inferior also in terms of the workability. Also, the productivity was reduced due to a so-called cycle time. Furthermore, the area occupied by the components other than the electron emission portions 5a increases, which may reduce the electron emission efficiency.